Manfuacture of artificial filaments, threads, ribbons, films, and other artificial products



Patented May 5, 1936 UNITED STATES PATENT OFFICE Henry Dreyfus, London,England No Drawing. Application July 13, 1933, Serial No. 680,253. InGreat Britain July 14, 1932 '7 Claims.

This application is a continuation in part of my application S. No.495,138 filed 12th November, 1930 and relates to the manufacture ofartificial filaments, threads, yarns, ribbons, films and the like and tofabrics and similar materials made from or containing such products, andmore particularly to the manufacture of such products having a reduced,subdued or modified lustre.

My application S. No. 495,138 describes processes wherein finely dividedfibrous materials are incorporated in the spinning solutions, suchfibrous material being insoluble in the spinning solution to which it isadded. The fibrous material is, therefore, of a different nature fromthe base of the spinning solution. Any type of organic fibrous materialmay be employed. Such materials may be natural materials, as for examplecotton, linen, straw and other vegetable cellulosic materials, silk,wool and other animal fibres, or artificial materials such asregenerated cellulose or cellulose derivative fibres. The fibrousmaterials should be incorporated in the spinning solution in a very finestate of subdivision. Several processes are described for obtaining thefibrous materials in a finely divided form; for example the organicfibrous material may be ground in a suitable mill with or without theadmixture of small or large quantities of suitable liquids, e. g. water,acetone or other liquids, used for dissolving the viscose, celluloseacetate or other base. The organic fibrous material may moreover beground in admixture with the base and in the presence or absence ofsuitable liquids. In this last process the product is dissolved in asuitable solvent and the solution so obtained contains the organicfibrous material in a finely divided form. Again, the organic fibrousmaterials may be reduced to a fine state by atomizing their solutionsinto a suitable drying or coagulating medium; for example a solution ofviscose may be atomized into a hot atmosphere preferably containing acoagulating agent such as gaseous hydrochloric acid, or a solution of acellulose derivative in a volatile solvent may be atomized into anevaporative atmosphere.

I have now discovered that particularly good results may be obtained inthe above processes by using organic fibrous material which has beenprepared in a very fine state of sub-division by precipitation fromsolution. The organic fibrous material may be of any kind, eithernatural or artificial and it may be dissolved in any suitable solvent.Thus, for example, cellulosic material which has been dissolved insulphuric acid, zinc chloride, thiocyanates, Schweitzers reagent orother solvents may be precipitated from its solution by suitable means.Again, cellulose may be precipitated from a viscose solution andcellulose derivatives such as cellulose esters and ethers, e. g.cellulose acetate, cellulose formate, cellulose propionate, cellulosebutyrate, cellulose benzoate, methyl, ethyl and b-enzyl cellulose, maybe precipitated from their solutions in suitable solvents.

Precipitating agents may be used which cause precipitation by virtue oftheir diluent action on the solvent, or which react with the solvent.

I have further discovered that cellulose benzoates, particularlydibenzoyl cellulose, prepared in a finely divided condition, are ofconsiderable value in delustring artificial textile materials of thecellulosic type such as viscose, nitrocellulose, or cuprammonium silks,and also textile materials made of certain cellulose derivatives withwhich they are incompatible or incompletely compatible, e. g.acetone-soluble cellulose acetate, ethyl cellulose acetate, and oxyethylcellulose acetate. The dibenzoyl cellulose or other cellulose benzoatemay be prepared in a finely divided condition by any suitable means, e.g. by grinding, or atomizing from solution or by any other of themethods described in application S. No. 495,138, or may veryadvantageously be prepared in a finely divided state by precipitationfrom solution in accordance with the processes described in thisapplication.

I prefer to carry out the precipitation by treating the solution of thefibrous material with precipitating agents, at normal or elevatedtemperatures, though in some cases a heat treatment may itself besufficient to cause precipitation. Cellulose may be precipitated fromits solution in mineral acids, such as sulphuric acid, hydrochloricacid, or'mixed acids, by means of water or solutions of salts such asalkali chlorides or sulphates. It is preferable to carry out thisprocess on freshly prepared solutions, and it is also preferable toprepare such solutions at low temperature in order to avoid unduedegradation of the cellulose molecule. Solutions of cellulose in zincchloride may also be precipitated by water, dilute acids or otherdiluents, for example alco hol. If the precipitate obtained from zincchloride solutions contains zinc compounds they may be removed bytreatment with suitable dilute acids. Cuprammonium solutions ofcellulose may be treated with salts, acids, alkalies and othersubstances, for example sugar, to precipitate the cellulose, and anycopper compounds contained in the precipitated cellulose may afterwardsbe removed by suitable reagents. Cellulose may be precipitated fromviscose solution by the action of acid reagents, and cellulosederivatives may be precipitated from their solutions by theincorporation therewith of non-solvents for the cellulose derivatives.Thus, for example, a solution of dibenzoyl cellulose in an organicsolvent may be precipitated in a fine state of sub-division by additionof a suitable non-solvent diluent, for example a hydrocarbon or anether.

Where the cellulose or cellulose derivative is to be precipitated bymeans of a liquid agent, I have found that good results may be obtainedby agitating or stirring the precipitating liquid. Agitation may beachieved by means of a nozzle delivering the solution of cellulose orcellulose derivative, or stirring or agitating means may be disposed inthe precipitating liquid. In addition the solution of the cellulose orcellulose derivative and also the precipitant may be heated, if desired,in any suitable manner as for example by means of a water or steamjacket or by direct heating. Alternatively, the precipitating agent maybe squirted through a nozzle situated under the solution under similarconditions. Furthermore the cellulosic material may be precipitated bygaseous means. Thus, cellulose may be precipitated from its cuprammoniumsolution by means of hydrochloric acid gas, or carbon dioxide, byforcing the precipitating gas through a spraying nozzle into thecellulosic liquid. In this case the movement of the gas may itself givesufficient stirring motion to'the solution, or the solution may befurther agitated by mechanical means.

Solutions of cellulose derivatives in organic solvents may be treatedwith non-solvents to precipitate the cellulose derivative in a finelydivided form. In this case it may be suflicient merely to incorporatethe non-solvent with the either hot or cold cellulose derivativesolution whilst stirring, without the aid of squirting nozzles or othersimilar apparatus. Vigorous agitation will result in the precipitationof the cellulose derivative in a finely divided form. Advantageously thesolution of the cellulose derivative in an organic solvent, whichsolution may be that in which the cellulose derivative has been preparedor may be any other suitable solution, may be brought to a point justshort of precipitation by means of a suitable amount of precipitatingmedium and then incorporated with a further quantity of precipitatingmedium. Thus for example cellulose may be esterified with aceticanhydride and acetic acid in the usual manner, the esterificationsolution brought to a point just short of precipitation with diluteacetic acid and the so-treated esterification solution precipitated witha large bulk of water or dilute acetic acid. The physical condition inwhich the materials are precipitated may to some extent be controlled bythe degree of agitation employed and, in general, more vigorousagitation will result in the precipitation of the cellulose derivativein a more finely divided form.

Where cellulosic material is precipitated from its solution by means ofdiluents or other precipitating media the operation may be carried outin the presence of agents calculated to inhibit agglomeration of theprecipitated particles, e. g. mild dispersing agents or protectivecolloids. Thus for example the precipitation may be carried out in thepresence of organic sulphonic acidsor gelatin, glue and the like. Ingeneral, however, it is preferable only to employ small quantities ofsuch agents.

The precipitated cellulosic material may be freed from the solvent andprecipitation liquors by filtration or ultra-filtration, or my besubjected to dialysis so that the precipitation and solvent liquors arereplaced by water. The water may then be replaced, if desired, withacetone or other suitable organic solvent or the aqueous suspension maybe employed directly in making up spinning solutions.

In another form of the invention cellulose or a cellulose derivative maybe precipitated actually in the spinning solution. Thus for example asolution of cellulose acetate in an organic solvent may be incorporatedwith a viscose spinning solution so as to precipitate the celluloseacetate throughout the mass in a finely divided condition.

Spinning solutions containing the finely divided fibrous materialsprepared according to the present invention may be spun by any suitableprocess, for example the processes described in application S. No.495,138 already referred to, according to the nature of the spinningsolution employed.

Example 1 10 parts of cellulose, for example in the form of purifiedwood pulp, are dissolved in 50-60 parts of strong sulphuric acid. Thesolution is preferably prepared at low temperatures, e. g. attemperatures of 0-10 0., in order to reduce degradation of the cellulosemolecule. The solution is diluted with water to a point just short ofthat at which precipitation would occur and is then injected as a finespray into a concentrated solution of sodium sulphate, the solutionbeing vigorously agitated during the addition. The suspension of finelydivided cellulose in the precipitating medium thus obtained may betransferred to a dialyzer and freed from sodium sulphate and sulphuricacid by means of water. The fine aqueous suspension is centrifuged inorder to concentrate the precipitate as much as possible and the waterof the resulting suspension is replaced by acetone by any convenientmethod, as for example by successively diluting the suspension withacetone and centrifuging. The acetone suspension is then employed inpreparing a solution of cellulose acetate in acetone, and the proportionof cellulose thus incorporated in the spin ning solution is adjusted tobe about 3-5% calculated on the weight of the cellulose acetate. Thisspinning solution is spun in any suitable manner either by dry or wetspinning methods and the filaments produced possess a subdued lustre.

Example 2 A 10% solution of dibenzoyl cellulose in chloroform is sprayedinto an excess of alcohol, the operation beihg carried out with vigorousstirring of the precipitating liquor. The dibenzoyl cellulose is thusprecipitated in a finely divided form and is separated from the bulk ofthe liquors by centrifuging. The finely divided dibenzoyl cellulose isincorporated into a viscose spinning solution to the extent of about 3%calculated on the base of the viscose solution. Filaments prepared fromthis solution possess a subdued lustre.

The term cellulosic material in this specification, unless the contextotherwise requires, and in the claims, is to be construed as coveringnot only cellulose itself but conversion products thereof such asoxycellulose and hydrocellulose and derivatives of cellulose, such asviscose, and cellulose esters or ethers.

What I claim and desire to secure by Letters Patent is:-

1. Artificial filaments, threads, ribbons, films and the like having abasis of cellulosic material incompatible with cellulose benzoate andcontaining finely divided cellulose benzoate.

2. Artificial filaments, threads, ribbons, films and the like having abasis of cellulosic material incompatible with dibenzoyl cellulose, andcontaining finely divided dibenzoyl cellulose.

3. Artificial filaments, threads, ribbons, films and the like having abasis of an organic derivative of cellulose incompatible with dibenzoylcellulose and containing finely divided dibenzoyl cellulose.

4. Artificial filaments, threads, ribbons, films and the like having abasis of cellulose acetate incompatible with dibenzoyl cellulose andcontaining finely divided dibenzoyl cellulose.

5. A spinning solution for use in the manufacture of artificialfilaments, threads, and the like which comprises a cellulosic materialdissolved in a suitable solvent therefor and which contains, as adisperse phase, a finely divided cellulose benzoate which isincompatible with the said cellulosic material.

6. A spinning solution for use in the manufacture of artificialfilaments, threads, and the like which comprises an organic derivativeof cellulose dissolved in a suitable solvent therefor and whichcontains, as a disperse phase, a finely divided dibenzoyl cellulosewhich is incompatible with the said organic derivative of cellulose.

7. A spinning solution for use in the manufacture of artificialfilaments, threads, and the like which comprises cellulose acetatedissolved in a suitable solvent therefor and which contains, as adisperse phase, finely divided dibenzoyl cellulose which has beenobtained in a finely divided form by precipitation from solution.

HENRY DREYFUS.

